Boil a beetroot and watch what happens. The water turns a deep pink-red, and the beetroot itself fades to a duller, tired maroon. Roast it and the edges go almost brown. Deep fry a slice and the colour drains out faster than you'd expect. Yet a bag of vacuum cooked beetroot chips holds onto that bright, almost stained-glass red all the way from the cooker to your snack bowl. The difference isn't the beetroot. It's the heat.
Why does beetroot lose its colour when cooked?
Beetroot gets its colour from a group of water-soluble compounds called betalains, most notably one called betanin. Betanin is naturally unstable, it breaks down when exposed to heat, light, and oxygen, and the higher the temperature and the longer the exposure, the faster that breakdown happens. Research on betalain stability has found that meaningful pigment loss starts showing up once beetroot is processed anywhere between roughly 50°C and 120°C, a range that covers most conventional cooking methods, including boiling, roasting, and standard deep frying. That's the entire story in one line: heat degrades the pigment, and most cooking methods use more heat, for longer, than the pigment can survive intact.
Meet betalain, the pigment doing all the work
Betalains are the class of pigments responsible for the red and yellow colours found in a specific group of plants, including beetroot, and betanin is the dominant one in red beetroot specifically. It's water soluble, which is exactly why beetroot bleeds so readily into anything wet around it, whether that's boiling water, a cutting board, or your hands. Because it's a dye that lives in water, it's also chemically sensitive. Heat breaks the molecule's structure apart. Light and oxygen do the same thing over a longer timescale, which is why cut beetroot left out on a counter also dulls over time even without any cooking involved.
None of this is unique to beetroot as a category of food. Plenty of pigments in fruits and vegetables are heat sensitive to some degree. Betalain is simply on the more fragile end of that spectrum, which is exactly why the cooking method chosen for beetroot matters more than it does for something like a carrot or a potato.
Why deep frying is especially hard on beetroot's colour
Deep frying typically runs past 160°C, and the beetroot slice sits in that heat long enough to cook through completely. For betanin, that's close to worst-case conditions, high temperature sustained over real time, with oxygen from the surrounding oil in constant contact with the beetroot's surface. The colour doesn't survive that combination well. By the time a conventionally fried beetroot chip is done cooking, a meaningful share of its original pigment has already broken down, which is part of why fried beetroot chips often come out browner or duller than the raw slice they started from.
How vacuum cooking is a different game
Vacuum cooking works by lowering the air pressure inside the cooking chamber, which in turn lowers the temperature needed to cook the beetroot through completely. Instead of frying at high heat the way conventional methods do, the process happens at a noticeably gentler temperature range, closer to what you'd use for slow drying than for deep frying. Less heat and less time under thermal stress means less opportunity for betanin to break down before the chip is fully cooked.
A study published in the Journal of Food Science and Technology examined this directly, testing how adjustments to temperature, pressure, and frying time during vacuum frying affected betalain retention in beetroot chips, alongside texture measures like oil content and breaking force. The research approached it as an optimisation problem, tuning those three variables together to find conditions that preserved pigment while still producing the texture expected of a proper chip. The underlying logic lines up with what's already known about betanin's heat sensitivity: gentler thermal conditions leave more of the original pigment intact than high-heat frying does.
What the research says about heat and colour retention
| Cooking condition | Approximate temperature | Effect on betalain pigment |
|---|---|---|
| Boiling | Around 100°C, sustained | Significant pigment loss, colour visibly leaches into water |
| Deep frying | Typically above 160°C | Rapid pigment breakdown, duller or browner finished colour |
| Roasting | Variable, often 180°C or higher | Pigment loss concentrated at the surface, browning at edges |
| Vacuum cooking | Lower temperature range under reduced pressure | Better pigment retention, colour closer to raw beetroot |
What this actually means in the bag
It means the deep red colour of a vacuum cooked beetroot chip isn't added back in, dyed on, or a trick of the packaging. It's what's left when the colour isn't cooked out of the beetroot in the first place. The betanin that gives raw beetroot its colour is mostly still there, just now sitting inside a crisp, cooked chip instead of a soft, boiled slice or a pale, over-fried one.
This is also why beetroot chip colour can vary a little from batch to batch. Betanin content in raw beetroot itself depends on factors like the specific beetroot and how it was grown, so even under identical cooking conditions, two batches won't be pixel-identical in shade. What stays consistent is the cooking approach, low temperature, low pressure, minimal time under heat stress, which is the part that determines how much of that natural colour survives the process at all.
Why colour retention isn't just about looks
It's easy to file bright colour under "looks nice in the photo" and move on, but for a food like beetroot, colour is one of the more honest signals available about how something was cooked. Betanin doesn't survive careless handling. It needs specific conditions, moderate temperature, limited time under heat, minimal oxygen exposure, to stay mostly intact. A beetroot product that holds onto that colour is, by definition, one that went through a process built around not damaging the pigment in the first place.
That's a useful way to think about vacuum cooking generally, not just for beetroot. The same low-temperature, low-pressure approach that protects betanin also tends to be gentler on the beetroot's texture and its other naturally occurring compounds, since none of them are being blasted with sustained high heat either. Colour just happens to be the one you can see without a lab test. Everything else that heat is hard on is happening in the background, whether or not it shows up as a visible change.
See that colour for yourself in Chaat Masala Beetroot and Sweet Chili Beetroot, both made the same vacuum cooked way.
Frequently asked questions
Why does boiled beetroot turn a duller colour than raw beetroot?
Boiling exposes beetroot to sustained heat around 100°C, which breaks down betanin, the water-soluble pigment responsible for beetroot's red colour. Because betanin is water soluble, a portion of it also leaches directly into the boiling water, which is why the water itself turns bright pink-red while the beetroot dulls.
Is the red colour in beetroot chips added artificially?
No. The colour in vacuum cooked beetroot chips comes from betanin, the pigment naturally present in raw beetroot. Nothing is added to enhance or restore colour, the gentler cooking process simply preserves more of what was already there.
Does the colour of a beetroot chip tell you anything about how it was cooked?
Generally, yes. Because betanin degrades predictably with heat exposure, a beetroot chip that holds a bright red colour close to raw beetroot typically indicates a lower-temperature cooking process, while duller or browner tones usually point to higher heat, longer cooking time, or both.
Does betanin break down over time even after cooking?
Yes. Betanin remains sensitive to light and oxygen even after cooking is complete, which is why beetroot-based colour, in chips or otherwise, is best kept away from prolonged light exposure and sealed from air where possible to hold its colour longer.